Are there any issues with tetracycline inducible promoters popping on all of a s - (Feb/10/2014 )

I'm designing a transgene that contains cre recombinase under the control of a tet inducible promoter. This entire transgene will be flanked by lox P sites. Therefore, this transgene will negative regulate itself. I'm just concerned about this promoter getting turned by other factors. I know tetracycline is found in some FBS, so I will need to use verified tet-free FBS. Are there any other caveats to this method?

-Ahrenhase-

I've found tet inducible promoters to be a bit leaky in mammalian cell culture, so even in the absence of tet you are likely to get a low level expression.

-bob1-

I've found tet inducible promoters to be a bit leaky in mammalian cell culture, so even in the absence of tet you are likely to get a low level expression.

I know there are DEX/DOX systems that allow for tighter control. I wanted to avoid DEX because of off-target effects it may have. DOX has off target effects too, but I figured my cell cultures are seeing DOX in the media (which contains FBS) anyway.